1. Field of the Invention
The present invention relates to a bi-directional optical transceiver module, and more particularly to a bi-directional optical transceiver module including an optical transmitter and an optical receiver, each of which having a TO-can structure.
2. Description of the Related Art
A bi-directional optical transceiver module performs transmission and reception of optical signals having different wavelengths. Conventional bi-directional optical transceiver modules have a structure in which an optical transmitter and an optical receiver are mounted in a single housing or on a single substrate.
The optical transmitter and optical receiver included in such a bi-directional optical transceiver module may have a butterfly structure or a TO-can structure. Optical transceiver modules, which include an optical transmitter and an optical receiver each having a TO-can structure, are usable for short-distance communication networks because they are inexpensive due to the low manufacturing costs of the TO-can structure.
FIG. 1 is a schematic diagram illustrating the configuration of a conventional bi-directional optical transceiver module. As shown in FIG. 1, the conventional bi-directional optical transceiver module includes an optical transmitter 110, which has a TO-can structure, that generates a first optical signal. The bi-directional optical transceiver module also includes an optical receiver 120, which has a TO-can structure, that detects a received second optical signal. The bi-directional optical transceiver module further includes an optical fiber ferrule 130 to input and output the first and second optical signals. The conventional bi-directional optical transceiver module also includes a filter 160 to divide optical paths of the first and second optical signals, and first through third lens systems 140, 150 and 170 to collimate or converge the first and second optical signals.
Generally, the first and second optical signals use different wavelength bands, respectively. For example, the first optical signal uses a C-band, and the second optical signal uses an L-band, the wavelength space between the first and second optical signals is about 17nm, which is very narrow. As a result, the filter must be aligned to have an angle of not more than 10° with respect to the optical path of the first optical signal.
When the wavelength space between the first and second optical signals is narrow, the second optical signal reflected from the filter forms a very small angle with respect to the optical path of the first optical signal. As a consequence, the optical paths of the first and second optical signals must be lengthened to implement a bi-directional optical transceiver module. This causes an increase in total volume.
FIG. 2 is a schematic diagram illustrating the configuration of another conventional bi-directional optical transceiver module. As shown in FIG. 2, this conventional bi-directional optical transceiver module includes an optical transmitter 210 that generates a first optical signal and an optical receiver 220 that detects a second optical signal. Both the optical transmitter 210 and the optical receiver 220 have a TO-can structure. The bi-directional optical transceiver module also includes an optical fiber ferrule 230, a filter 260, a mirror 280, first through third lens systems 240, 250 and 270 to collimate or converge the first and second optical signals, and a housing 290.
The first lens system 240 collimates the first optical signal, and outputs the collimated first optical signal to the optical fiber ferrule 230. The second lens system 250 converges the first optical signal to one end of the optical fiber 231. The second lens system 250 also collimates the second optical signal, and outputs the collimated second optical signal to the filter 260. The third lens system 270 converges the second optical signal to the optical receiver 220.
The filter 260 is arranged between the optical transmitter 210 and the optical fiber 231 to output the first optical signal generated from the optical transmitter 210 to the optical fiber 231. The filter 260 also reflects the second optical signal received from the optical fiber 231 so that the second optical signal has a predetermined angle with respect to the first optical signal.
The mirror 280 reflects the second optical signal reflected from the filter 260 toward the optical receiver 220. The mirror 280 and filter 260 are aligned with each other in the housing 290 with respect to optical axes thereof. The filter 260 is arranged to have a predetermined angle with respect to the optical path of the first optical signal.
In this arrangement, however, the reflection angle of the second optical signal may vary greatly depending on the alignment error of the filter. Furthermore, since the constituent elements of the bi-directional optical transceiver module are integrally formed in the single housing, it is difficult to easily achieve a desired optical axis alignment. Also, misalignment of optical axes may easily occur during the optical axis alignment process.